[gthumb: 66/129] jpeg utils: added _jpeg_exif_orientation()

[Paolo Bacchilega <paobac src gnome org>]

commit 0dea5ea2ba374b68a1357c7116dede8b77e1d7ad
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Sun Apr 24 11:09:01 2011 +0200

    jpeg utils: added _jpeg_exif_orientation()

 extensions/jpeg_utils/Makefile.am             |    2 +
 extensions/jpeg_utils/jpeg-exif-orientation.c |  189 +++++++++++++++++++++++++
 extensions/jpeg_utils/jpeg-exif-orientation.h |   30 ++++
 3 files changed, 221 insertions(+), 0 deletions(-)
---
diff --git a/extensions/jpeg_utils/Makefile.am b/extensions/jpeg_utils/Makefile.am
index a8088de..5efee06 100644
--- a/extensions/jpeg_utils/Makefile.am
+++ b/extensions/jpeg_utils/Makefile.am
@@ -7,6 +7,8 @@ libjpeg_utils_la_SOURCES = 		\
 	jmemorydest.h			\
 	jmemorysrc.c			\
 	jmemorysrc.h			\
+	jpeg-exif-orientation.c		\
+	jpeg-exif-orientation.h		\
 	jpegtran.c			\
 	jpegtran.h			\
 	transupp.h			\
diff --git a/extensions/jpeg_utils/jpeg-exif-orientation.c b/extensions/jpeg_utils/jpeg-exif-orientation.c
new file mode 100644
index 0000000..c2f511e
--- /dev/null
+++ b/extensions/jpeg_utils/jpeg-exif-orientation.c
@@ -0,0 +1,189 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
+
+/*
+ *  GThumb
+ *
+ *  Copyright (C) 2011 Free Software Foundation, Inc.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#include <config.h>
+#include "jpeg-exif-orientation.h"
+
+
+GthTransform
+_jpeg_exif_orientation (guchar *in_buffer,
+			gsize   in_buffer_size)
+{
+	int       pos = 0;
+	guint     length;
+	gboolean  is_motorola;
+	guchar   *exif_data;
+	guint     offset, number_of_tags, tagnum;
+	int       orientation;
+
+	/* Read File head, check for JPEG SOI + Exif APP1 */
+
+	if ((in_buffer[pos++] != 0xFF)
+	    || (in_buffer[pos++] != 0xD8)
+	    || (in_buffer[pos++] != 0xFF)
+	    || (in_buffer[pos++] != 0xE1))
+	{
+	    return 0;
+	}
+
+	if (in_buffer_size < 2)
+		return 0;
+
+	/* Length includes itself, so must be at least 2 */
+	/* Following Exif data length must be at least 6 */
+
+	length = ((guint) in_buffer[pos] << 8) + ((guint) in_buffer[pos + 1]);
+	if (length < 8)
+		return 0;
+
+	pos += 2;
+
+	/* Read Exif head, check for "Exif" */
+
+	if ((in_buffer[pos++] != 0x45)
+	    || (in_buffer[pos++] != 0x78)
+	    || (in_buffer[pos++] != 0x69)
+	    || (in_buffer[pos++] != 0x66)
+	    || (in_buffer[pos++] != 0)
+	    || (in_buffer[pos++] != 0))
+	{
+		return 0;
+	}
+
+	/* Length of an IFD entry */
+
+	if (length < 12)
+		return 0;
+
+	exif_data = in_buffer + pos;
+
+	/* Discover byte order */
+
+	if ((exif_data[0] == 0x49) && (exif_data[1] == 0x49))
+		is_motorola = FALSE;
+	else if ((exif_data[0] == 0x4D) && (exif_data[1] == 0x4D))
+		is_motorola = TRUE;
+	else
+		return 0;
+
+	/* Check Tag Mark */
+
+	if (is_motorola) {
+		if (exif_data[2] != 0)
+			return 0;
+		if (exif_data[3] != 0x2A)
+			return 0;
+	}
+	else {
+		if (exif_data[3] != 0)
+			return 0;
+		if (exif_data[2] != 0x2A)
+			return 0;
+	}
+
+	/* Get first IFD offset (offset to IFD0) */
+
+	if (is_motorola) {
+		if (exif_data[4] != 0)
+			return 0;
+		if (exif_data[5] != 0)
+			return 0;
+		offset = exif_data[6];
+		offset <<= 8;
+		offset += exif_data[7];
+	}
+	else {
+		if (exif_data[7] != 0)
+			return 0;
+		if (exif_data[6] != 0)
+			return 0;
+		offset = exif_data[5];
+		offset <<= 8;
+		offset += exif_data[4];
+	}
+
+	if (offset > length - 2) /* check end of data segment */
+		return 0;
+
+	/* Get the number of directory entries contained in this IFD */
+
+	if (is_motorola) {
+		number_of_tags = exif_data[offset];
+		number_of_tags <<= 8;
+		number_of_tags += exif_data[offset+1];
+	}
+	else {
+		number_of_tags = exif_data[offset+1];
+		number_of_tags <<= 8;
+		number_of_tags += exif_data[offset];
+	}
+	if (number_of_tags == 0)
+		return 0;
+
+	offset += 2;
+
+	/* Search for Orientation Tag in IFD0 */
+
+	for (;;) {
+		if (offset > length - 12) /* check end of data segment */
+			return 0;
+
+		/* Get Tag number */
+
+		if (is_motorola) {
+			tagnum = exif_data[offset];
+			tagnum <<= 8;
+			tagnum += exif_data[offset+1];
+		}
+		else {
+			tagnum = exif_data[offset+1];
+			tagnum <<= 8;
+			tagnum += exif_data[offset];
+		}
+
+		if (tagnum == 0x0112) /* found Orientation Tag */
+			break;
+
+		if (--number_of_tags == 0)
+			return 0;
+
+		offset += 12;
+	}
+
+	/* Get the Orientation value */
+
+	if (is_motorola) {
+		if (exif_data[offset + 8] != 0)
+			return 0;
+		orientation = exif_data[offset + 9];
+	}
+	else {
+		if (exif_data[offset + 9] != 0)
+			return 0;
+		orientation = exif_data[offset + 8];
+	}
+
+	if (orientation > 8)
+		orientation = 0;
+
+	return (GthTransform) orientation;
+}
diff --git a/extensions/jpeg_utils/jpeg-exif-orientation.h b/extensions/jpeg_utils/jpeg-exif-orientation.h
new file mode 100644
index 0000000..22ea462
--- /dev/null
+++ b/extensions/jpeg_utils/jpeg-exif-orientation.h
@@ -0,0 +1,30 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */
+
+/*
+ *  GThumb
+ *
+ *  Copyright (C) 2001-2009 The Free Software Foundation, Inc.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef JPEG_EXIF_ORIENTATION_H
+#define JPEG_EXIF_ORIENTATION_H
+
+#include <gthumb.h>
+
+GthTransform  _jpeg_exif_orientation (guchar *in_buffer,
+				      gsize   in_buffer_size);
+
+#endif /* JPEG_EXIF_ORIENTATION_H */